For Antarctic food webs, penguin poo is the gift that keeps on giving
Study finds wind-blown faecal matter boosts inland ecosystems. Natalie Parletta reports.
Nitrogen-rich droppings from penguins and seals along the Antarctic Peninsula fuel biodiversity hotspots that stretch several kilometres inland, researchers reveal in a paper published in the journal Current Biology.
“What we see is that the poo produced by seals and penguins partly evaporates as ammonia,” explains lead author Stef Bokhorst from the University of Amsterdam in the Netherlands.
The ammonia is picked up by the wind and blown inland where it enriches the soil, providing the nitrogen that algae and fungi, primary producers that underpin local food webs, need to survive in the harsh landscape.
The oceans surrounding Antarctica are some of the most productive and unspoiled on Earth, supporting a rich abundance of marine life.
Millions of penguins from several species, as well as elephant seals (Mirounga leonina), source their food in the water, then digest it, and excrete its waste products, back on land.
Although researchers had previously noted that the presence of birds and seals assists plant growth and soil respiration in the immediate area, until now there had been little attention paid to the impact of nitrogen on the broader Antarctic food web.
Globally, nitrogen delivered by bird droppings is an important nutrient source for different habitats.
Even just a short distance in from the coast Antarctic Peninsula coast, conditions are drier and harsher. Ecosystems comprise base-level mosses and lichens, supporting populations of tiny invertebrates such as springtails (from the genus Collembola), mites (Acari), nematode worms and water bears, or tardigrades.
To investigate the impact of nutrient input on these inland networks, Bokhorst and colleagues travelled along the peninsula coast, from the South Orkney Islands to Marguerite Bay, collecting soil and plant specimens.
After many months counting and identifying the samples, back in the lab, they found that springtails, mites and roundworms were up to eight times more abundant within six kilometres of penguin and seal colonies.
In fact, there were millions of the small invertebrates per square metre. Numbers dropped off sharply as distance from colonies increased.
Extrapolating from their findings and existing penguin population data, the researchers predict that the poo-boosting effect extends the full length of the maritime Antarctic.
The penguin and elephant seal colonies create an important nutrient conduit between the ocean and land, Bokhorst says.
“In a sense, the productivity of the ocean biome spills over onto the land,” he adds.
It suggests that “processes regulating community assembly, beyond temperature and water availability, also apply on the coldest continent on Earth”, the authors write.